Seedling-aided cache detection by heteromyid rodents

Heteromyid rodents are granivores which frequently cache seeds in numerous scattered locations and use olfaction to relocate these caches. However, se edlings which emerge from these caches may also serve as cues to cache loca tion. We conducted an experiment in the western Great Basin to determine wh ether heteromyids perceive emerging seedlings of Indian ricegrass, Achnathe rum hymenoides, as beacons to cache locations. Specifically, we compared fr equencies with which heteromyids searched for seeds among locations differi ng in the presence or absence of buried seeds and aboveground seedling trea tments, which included either a single Indian ricegrass seedling or an arti ficial seedling proxy. The olfactory cue related to seeds was clearly impor tant in relocating caches, as digging by heteromyids near artificial seedli ngs and at control locations lacking seedlings was significantly more likel y if seeds were present. However, rodents dug for seeds near natural seedli ngs at similar frequencies regardless of whether a seed cache was actually present at the base of the seedling. Moreover, seeds had no effect on the f requency at which rodents exhibited investigative, superficial digging beha vior near artificial seedlings. The latter results indicate that heteromyid s do associate emerging seedlings with cache locations, and that this assoc iation may primarily be a beacon to potential cache locations. Seedling-aid ed cache detection is important because it could improve the effectiveness of cache-searching behavior during a period when recovery of caches is crit ical for survival.